The present invention relates to an improved method for making platinum-phosphine complexes and to certain platinum-phosphine-vinylsiloxane complexes.
The term platinum-phosphine complexes and platinum-phosphine-vinylsiloxane complexes, as used herein refers to complexes wherein the platinum atom in the complex has a formal oxidation state of zero.
Platinum-phosphine complexes have been known for many years. For example, Malatesta et al., Journal of the Chemical Society, 1957, 1186, disclose the synthesis of platinum-phosphine complexes.
Exemplary of known methods for making platinum-phosphine complexes is the reduction of a phosphine-complexed platinous chloride, said reduction being performed by a mixture of hydrazine, alcoholic potassium hydroxide, and an excess of non-complexed phosphine. Another known method, suitable for making trialkylphosphine complexes of platinum, is the displacement of boroallyl ligands on platinum by phosphines.
Another known method uses platinum-phosphine-olefin complexes as starting materials. An example of this method is the work of Fitch et al., as disclosed in the Journal of Organometallic Chemistry, 1978, 160, 477. Fitch et al. reacted vinylsilanes with platinum-phosphine-olefin complexes wherein the vinylsilanes have the general formula CH.sub.2 .dbd.CHSi(CH.sub.3).sub.y (OC.sub.2 H.sub.5).sub.3-y, y having a value of 0, 1, 2 or 3.
Each of these known methods of making platinum-phosphine complexes is fraught with difficulty: yields are low; starting materials are difficult to synthesize, difficult to handle and difficult to obtain; and the reactions are prone to side reactions in the presence of small amounts of contaminants. For example, small amounts of water can hydrolyze and cause condensation of the ethoxy-substituted vinylsilanes of Fitch et al., thus rendering Fitch et al's complexes either less useful, or totally useless.